In various kinds of plants, such as gas turbine power generation plants, nuclear power generation plants, and chemical plants, the quantity of state of the plant, such as temperature or pressure, is acquired from the plant in order to monitor whether or not the plant is normally operated. In monitoring the plant, it is necessary to monitor a plurality of state quantities and the tendency of the state quantities, and a skilled technique capable of determining whether or not the plant is normally operated is needed. The following Patent Citation 1 discloses a technique in which a plurality of reference spaces (referred to as unit spaces) is prepared for each season in a year and is used to correspond to a season variation, thereby monitoring the operation state of a refrigeration cycle apparatus based on the Mahalanobis distance. When this technique is applied to monitor the plant, it is possible to relatively easily monitor a plurality of state quantities.
[Patent Citation 1]
Japanese Unexamined Patent Application, First Publication No. 2005-207644